Mixed esters of polyphosphazenes

Abstract

A polyphosphazene hydraulic fluid that remains solids-free on storage at temperatures down to -30° C. over an extended period can be made by reacting a solution of sodium phenoxide, sodium m-methylphenoxide, sodium p-methylphenoxide and sodium trifluoroethoxide with a small stoichiometric excess of cyclic phosphonitrilic chloride oligomer, mainly trimer, and then reacting the remaining replaceable chlorine atoms with a solution of sodium trifluoroethoxide.

We claim: 
     
       1. A process for making a polyphosphazene hydraulic fluid that remains solids-free on storage at temperatures down to -30° C., said process comprising: (A) preparing a solution of about 0.2-0.3 mole parts of sodium phenoxide, 0.12-0.22 mole parts of sodium m-methylphenoxide, 0.02-0.15 mole parts of sodium p-methylphenoxide and 0.3-0.9 mole parts of sodium 2,2,2-trifluoroethoxide in an inert solvent, the total parts being about 0.85-0.95 moles for each equivalent of replaceable chlorine in the cyclic phosphonitrilic chloride oligomer,   (B) preparing a solution of about 0.2 mole parts of a cyclic phosphonitrilic chloride oligomer comprising predominantly trimer in an inert solvent,   (C) mixing the solution of step (A) with the solution of step (B),   (D) reacting the resultant mixture at a temperature in the range of ambient up to reflux until the reaction is substantially complete,   (E) preparing a solution of sodium 2,2,2-trifluoroethoxide in an inert solvent,   (F) in a second stage, mixing the trifluoroethoxide solution of step (E) with the reaction mixture of step (D), the amount of said trifluoroethoxide solution being an amount which when taken together with the sodium phenoxide, m-methylphenoxide, p-methylphenoxide and trifluoroethoxide of step (A), totals at least 1.01 mole parts per each equivalent of replaceable chlorine in said cyclic phosphonitrilic chloride oligomer,   (G) reacting the mixture at an elevated temperature up to reflux until substantially all replaceable chlorine has reacted and   (H) recovering the polyphosphazene hydraulic fluid.   
     
     
       2. A process of claim 1 wherein in step (C) the solution of step (A) is added to the solution of step (B). 
     
     
       3. A process of claim 2 wherein said inert solvent in steps (A) and (E) is an ether. 
     
     
       4. A process of claim 3 wherein said inert solvent in step (B) is cyclohexane. 
     
     
       5. A process of claim 1 wherein the amount of trifluoroethoxide solution added in step (F) is an amount which when taken together with the sodium phenoxide, m-methylphenoxide, p-methylphenoxide and trifluoroethoxide of step (A) totals about 1.01-1.05 mole parts per each equivalent of replaceable chlorine in said cyclic phosphonitrilic chloride oligomer. 
     
     
       6. A process of claim 5 wherein in step (C) the solution of step (A) is added to the solution of step (B) over an extended period of time. 
     
     
       7. A process of claim 6 wherein said inert solvent in steps (A) and (E) is tetrahydrofuran and said inert solvent in step (B) is cyclohexane. 
     
     
       8. A process of claim 7 wherein the solution in step (A) comprises 0.23-0.27 mole parts of sodium phenoxide, 0.15-0.2 mole parts of sodium m-methylphenoxide, 0.05-0.11 mole parts of sodium p-methylphenoxide and 0.5-0.7 mole parts of sodium 2,2,2-trifluoroethoxide. 
     
     
       9. A process for making a polyphosphazene hydraulic fluid that remains solids-free on storage at -30° C., said process comprising: (A) preparing a solution of about 0.25 moles of sodium phenoxide, 0.18 moles of sodium m-methylphenoxide, 0.08 moles of sodium p-methylphenoxide and 0.6 moles of sodium 2,2,2-trifluoroethoxide in tetrahydrofuran,   (B) preparing a solution of about 0.2 mole parts of cyclic phosphonitrilic chloride trimer in cyclohexane,   (C) adding the solution of step (A) to the solution of step (B) over an extended period of time,   (D) heating the resultant mixture at reflux,   (E) preparing a solution of about 0.13 mole parts of sodium 2,2,2-trifluoroethoxide in tetrahydrofuran,   (F) mixing the solution of step (E) with the reaction mixture of step (D),   (G) heating the mixture at reflux until substantially all replaceable chlorine has reacted and   (H) recovering the polyphosphazene hydraulic fluid.   
     
     
       10. A polyphosphazene hydraulic fluid made by the process of claim 1. 
     
     
       11. A polyphosphazene hydraulic fluid made by the process of claim 2. 
     
     
       12. A polyphosphazene hydraulic fluid made by the process of claim 5. 
     
     
       13. A polyphosphazene hydraulic fluid made by the process of claim 6. 
     
     
       14. A polyphosphazene hydraulic fluid made by the process of claim 7. 
     
     
       15. A polyphosphazene hydraulic fluid made by the process of claim 8. 
     
     
       16. A polyphosphazene hydraulic fluid made by the process of claim 9.